Improvement in steam-engine slide-balance valves



@latent (attire.

l, JOHN F. WALLACE, OF BIRMINGHAM, PENNSYLVANIA.

Letters Patent No. 92,128, dated June 29, 1869.

IMPRovEMENT IN STEAM-ENGINE SLIDE-BALANGE VALVES.

The Schedule referred to in these Letters Patent and making part of the same.

To all whom 'it may concern Be it known that I, JOHN F. WALLACE, of Birmingham, in the county of Allegheny, and State of Pennsylvania, have,invented Aa new and useful Improvement in Balance Slide-Valve; and I do hereby declare the following to be a full, clear, andexaot description thereof, reference .being had to the accompanying drawing, making a part of this specification, iu which Figure 1 is a transverse vertical, and Figure 2, a longitudinal vertical sectionI of my im proved slide-valve, the latter as formed by a plane passing through the steam-chest parallel with the valve-stem, but a little in front of it.

-Likeletters of reference indicate like parts in each.

My invention relates to the .construction of an improved balance slide-valve for steam-engines, in which the downward pressure exerted by the steam on the valve is relieved 0r balanced.` by an opposite upward pressure; and

The nature of it consists in making the upper part of the valve of a T-shape. and interlocking therewith a slotted'box, or a box U-shaped, with inwardly-projecting edges, and attached to or forming a part of the balancing plunger, so that in operation, the'T of the former willslide or roll by interposed rollers on the projecting edges of the slotted box; and

lt further consists in the arrangement of the valve and plunger, 'so constructed, with one or more series of loose rollers, by which to convert sliding into rolling friction. f

. To enable others skilled in the art to make and use my invention, I will proceed to describe its construcf tion and mode of operation. A

a. represents the bottom plate of the steam-chest a of a steam-engine, having steam and exhaust-ports c c', all of the usual or any known construction.

b is a slide-valve, made with a lower face, to open and close theports c c', alternately, as it receives its throw from the stem b in either direction.

, Steam is admitted into the steam-chest a by a steam- Y pipe from the boiler.

Ordinarily, the pressure exerted by the steam on the valve b would be so great, that either the lower face of the vatte b, or its seat on the bottom plate a', or both, would speedily be worn or cut away, and "at the same time there would be a considerable 'waste of vpower in giving the valve the requisite throw.y l' hence make the upper part of the valve b of a T-shape, as shown at n..

On the lower part of the plunger f, I make a box, d, slotted in its lower side, so as to admit therein the neck ofthe T-part u of the `valve b, and the cavity of the box at least large enough to admit the head ofthe T, as shown in fig. l, d being the inwardly-projecting edges on either side of the slot-box referred to. The box d and valve bshould bel of about the same length.

Attached to the upper end of the box al is a balancmg-plunger, f, preferably of cylindrical shape, which plays through a stufiing-box, yy, in the upper part`= of the steam-chest a, the whole being enclosed by a cover,

g', and all the parts properly attached and connected.

The superlcial area ofthe cross-section of the plungl erf is somewhat less'than the area of the valve b, subject to the downward pressure of the steam. These `relative areas maybe so regulated at pleasure as to secure the end in View, which is to balance the downward pressure ofthe steam on the valve b, by-its upward pressure on the lower end of the plunger. j; but still to secure a downward pressure, suiliciently in excess of the upward pressure, to keep` the valve b well to its seat. y

It will be observed that while the .valveb plays back and-forth, the plunger f has no motion, except that produced by the upward pressure of the steam.

Toreduce frictionv .to a minimum, Iy interpose, between the two, one or more series of rollers, e, two or more in each series. y v

lhe under face ofthe head n of theTis chambered out `on each side of the. neckar?, 'to make room -for the operating of the rollers c therein. These rollers I make of such diameter, relative to the length of 'the stroke of thevalve b, that with each stroke the v rollers will make one ormore complete revolutions, as

near as may be; for if they each were to make a frac' tional partof a revolution, they would soon be worn out of a round or cylindrical shape. By the use. of such rollers', in the manner described, sliding is converted into rolling friction, and of course reduced to a minimum.

The cover g may have an interposed packing, s, andy the plunger f be screwed by a nut, s', down, so that the valve may be fairly seated; or, ou the other hand, Ithe steam-chest may be madewith atight cover, as in iig. 2, and a packing-cushion, of India rubber or otherlike yelastic con'xpressible4 material, m, maybe interposed be-k tween it andthe plunger f. The thickness ofthispack v ing should be such that the valve may come well down .f

on its seat, and at the same time should have suffi cient elasticity to permit of the balancing-action of the plunger, as above described.

What I claim as my invention, and desire to secure l. The construction, in detail,.of the slide-valve, balancing-plun ger, with the interposed loose rollers, all arranged substa-ntially as described.

2. The construction and' arrangement of the cover g', as shown in tig. 2, with an elastic packing, balanced plunger, slide-valve, and loose rollers, substantially as set forth. Y v p In testimony whereof, I, the said JOHN F. WALLACE, have hereunto set my hand. JOHN F. WALLACE.

Witnesses:

Taos. B. Kenn,

JOHN GLENN. I 

